The present invention pertains to tunneling machines. More specifically the present invention relates to convertible tunneling machines that employ a low flow of slurry to prevent tunnel face subsidence by creating a liquid balance, but not as a transport medium.
Diverse ground conditions are encountered in the excavation of some tunnels. Sand, marl, limestone, clays, and chalk may all be expected. At times, various types of ground may be encountered simultaneously. The water tables along a tunnel also vary considerably. This inconsistency of tunnel geology demands a convertible machine. In many of these ground conditions, support of the face is necessary to prevent ground settlement or the creation of excessive voids around the tunnel lining. In other areas face support is not necessary. Such a convertible machine that is fast and convenient to reconfigure does not exist in the prior art.
Effective methods of workface control commonly used to support unstable soil faces are the slurry and earth pressure balance (EPB) shield methods. A traditional slurry system requires a large surface plant with filter presses to remove fine clay particles suspended in a dilute slurry. In addition, a large diameter slurry discharge line must be continuously extended as the TBM (tunnel boring machine) advances. This discharge line typically runs the tunnel length to the surface plant.
The other conventional approach for workface control, earth pressure balance, eliminates the slurry discharge line and surface plant. The primary concern with a EPB system is the possibility of plugging inside the very large cutterhead, and for this reason the muck must be kept as fluid as possible. Fluid mixed with appropriate additives must be injected into the head to maintain the proper pressure to ensure face stability. The material most likely to cause plugging is moist clay, but its flowability characteristics can be improved by the addition of polymers. In addition, the torque requirements for cutterhead rotation for a large diameter cutterhead are extremely high for an EPB design. Thus, an adequate system for tunnel face control in unstable soil conditions is currently lacking in the prior art, even aside from the lack of convertability of the conventional slurry and EPB soft ground systems to a hard ground system when desired.
Tunneling machines previously known in the art that either employ a conventional slurry or an earth pressure balance system to control an unstable tunnel workface, or that operate in varying geological conditions, are described below.
United Kingdom Patent No. 1,083,322, issued to Bartlett, uses a tunneling apparatus including a shield containing or supporting a power driven rotary mechanical digging mechanism in front of a bulkhead, in which a liquid thixotropic suspension is delivered under pressure to the space in front of the bulkhead so as to contact the working face on which the digging mechanism acts and the spoil excavated by the digging mechanism is removed together with a proportion of the liquid suspension The material removed from the tunneling shield is partially cleaned or separated, and the cleaned constituent containing a high proportion of the thixotropic suspension is returned to the space in front of the bulkhead. The material removed from the shield is moved to a point at the rear, but within the formed portion of the tunnel, to be cleaned. The discharge duct is preferably at an elevated level in the bulkhead. One result of this construction, as broadly suggested by this patent, is that it may be possible, when conditions permit, to operate the shield as a conventional mechanical tunneling shield without the liquid suspension, and to remove spoil by means of a belt conveyor or the like.
U.S. Pat. No. 4,881,862, issued to Dick, discloses a screw seal having a conveying section feeding into a sealing section within a housing, wherein the sealing section has a divergent cross sectional area. The divergence is predetermined in conjunction with the compressibility and permeability of the bulk solids and the coefficient of friction between the solids and the barrel of the sealing section, so as to permit the formation of a sufficiently dense plug of the solids to form an effective gas seal, but to limit the solids pressures and thereby to control the resulting increase in driving torque. Other features comprise a number of variations in the structures of the conveying and sealing sections, and also the discharge chamber into which the sealing plug is driven. These permit a large variety of applications and with many different types of bulk solid materials.
U.S. Pat. No. 4,848,963, issued to Babendererde et al, discloses an earth pressure shield for a tunnel excavator having a front working compartment formed by a separating wall, having a digging tool and an annular reinforcing space substantially triangular in cross section positioned directly in front of the separating wall. So that extensive restructuring of the machine is not necessary when moving from soft roof to hard ground, the annular reinforcing space is provided with a lower fluid feeder, a controlled upper pressurized air feeder, a plurality of fluid connector pipes which are guided from below to an upper fluid outlet opening into the working compartment, and a fluid level controller.
U.S. Pat. No. 4,844,656, issued to Babendererde et al discloses an earth pressure shield having a front working compartment, having at least one digging or mining tool, and formed by a separating wall, in which an annular space is formed with a top region connected with a regulated pressurized air feed and with a bottom region opened to the digging or mining tool so that the dug or mined earth material is moved with the help of a conveyor unit. At least one fluid pipe is guided from a fluid chamber with a first level controller and with the fluid feeder to a fluid outlet opening to the digging or mining tool.
Behind the working compartment formed with an immersed wall, a bulkhead space is provided by partitioning. The bulkhead is connected in an upper region with the top region of the annular space by an opening in the separating wall and includes the fluid chamber in a lower region. In an additional partitioned chamber or space, a bulkhead space is provided to the rear of the working chamber in which the immersed wall is located and which partitions the front portion of the tunnel and/or digging machine. The drive for the digging wheel, the pressurized air feed for clearing the working compartment, mixing devices, and a screw conveyor all project through this bulkhead space. The lower and larger part of the bulkhead space is filled with water and/or a muck suspension, while the upper part is filled with compressed air which, because of the upper connection of the pressurized air cushion behind the immersed wall, stands under the same predetermined pressure as acts on the earth material behind the immersed wall.
The fluid pipe, which opens in the lower portion of the bulkhead space, guides water and/or the suspension through the upper part of the bulkhead space filled with pressurized air and through the pressurized air cushion located behind the immersed wall in the vicinity of the roof of the front part of the working compartment. Also, feeder means for water and/or suspension, which supply the bulkhead which is penetrated by the digging tool, is connected to the water filled bulkhead space.
The air cushion with a predetermined regulated pressure guarantees the same constant pressure on the earth material located behind the immersed wall and the water and/or suspension located in the partitioned portion. Measuring and control systems provide that the level of the earth material and the water itself are the same, i.e. at the same height. The shear resistance of the earth material in the working compartment prevents the predetermined supporting pressure in the pressurized air cushion from being transmitted to the local front wall, especially in the sensitive roof region. A zone of lower pressure arises in which the water and/or suspension flows into the roof region of the front part of the working compartment through the ducts from the bulkhead rear space.
A nonreturn valve opens only when the predetermined supporting pressure is not attained. Simultaneously the water and/or the suspension standing under the predetermined supporting pressure flows by feed means in the digging wheel into the space through which the digging tool travels in front of the digging wheel.
Mixing and stirring devices behind the immersed wall provide for a uniform mixing of the earth material with the delivered fluid. Regulated pressurized air feed is guided through the partition of the bulkhead space. To obtain the best possible mixing of the dug earth material with the fluid (water an/or suspension), at least one stirring unit is located in the bottom region of the working compartment behind the immersed wall. A nonreturn or check valve for the fluid outlet is provided so that a predetermined supporting pressure is not exceeded.
U.S. Pat. No. 4,818,026, issued to Yamazaki et al, discloses a device that transfers cut bedrock through the cutterhead to the tunneling machine interior. In a central area of the cutterhead compartment is provided a debris receiving chamber into which are channeled the front-end portion of a screw conveyor and the front-end portion of a water supply pipe. A rear-end portion of the water supply pipe is connected to a water-supply source disposed in a rear area of the tunneling apparatus. The water issues from such water supply source to the debris receiving chamber through its upper opening so that the cutterhead compartment is filled with water which buoys up the rock debris to enable the debris to easily enter the debris receiving chamber through its upper opening under the influence of the rotational movement of the cutterhead compartment. The rock debris received in the debris receiving chamber is transported rearwardly together with water by means of the screw element of the screw conveyor, reaching an outlet opening of an outer sleeve of the screw conveyor, and then dropping therefrom to a rock crusher.
U.S. Pat. No. 4,774,470, issued to Takigawa et al, is for a tunneling machine having electromagnetically based sensors that detect and display conditions of the tunnel earth. The invention includes an electromagnetic wave transmitting and receiving unit mounted on the top of the shield machine for radiating electromagnetic impulse waves towards the tunnel earth and for receiving the electromagnetic waves reflected from the tunnel earth. A position sensor collecting information regarding the position of the electromagnetic waves, wave transmitter and receiver unit is included. A data processing unit is provided for processing the signals from the transmitter/receiver and the position sensor as sent through a transmission line. The data processing unit continuously displays the condition of the tunnel earth at the cutting fact.
U.S. Pat. No. 4,630,869, issued to Akesaka et al discloses a shield tunneling machine having a partition wall. A lidded opening is formed in the upper portion of the partition wall. The lid is pivotally connected through an arm to the piston rod of a pneumatic or hydraulic cylinder mounted on the wall member and the cylinder keeps the opening normally closed. However, when the pressure of muck received in the space between the partition wall and the cutterhead exceeds the pressure sent to the cylinder, the lid moves pivotally toward the partition wall against the pressure of the cylinder to open the opening, permitting muck flow into the muck chamber. In the muck chamber are disposed a rotor and a stator constituting a crusher for crushing relatively large gravel entering the muck chamber. The rotor is mounted on a rotary shaft and the stator below the rotor is mounted on the partition wall. High pressure water is sent into the muck chamber through a water supply pipe and the supplied water is discharged from the muck chamber together with the muck to the rear portion of the shield body through a drain pipe.
This shield tunneling machine also comprises a tubular shield body, a partition wall provided in the shield body, a rotary shaft rotatably supported by the partition wall and extending along the axis of the shield body, a cutterhead disposed on the front end of the rotary shaft and including a first cutter provided with a plurality of cutter bits and a second cutter provided with a plurality of roller bits, a mechanism for rotating said cutterhead by means of a rotary shaft and a mechanism for relatively moving straight forward and backward one or the other of the first and second cutters. The cutter bits and roller bits are mounted respectively on the first and second cutters so that one of the cutter bits and roller bits can be projected and the other can be retracted for excavation according to the geology of the face. Thus, this shield tunneling machine can be used for excavating either soft or hard ground. Further, the roller bits do not hinder the excavating operation of the bits in excavating the soft layer and the cutter bits are not damaged by the excavating operation of the roller bits in excavating the hard layer.
U.S. Pat. No. 4,629,255, issued to Babendererde discloses a tunneling apparatus with a lateral shield having a front end normally engaged longitudinally against a tunnel end face, a digging tool at the front end of the shield and engageable with the tunnel face, and a drive for displacing the tool and digging the tunnel face. A transverse pressure wall across the shield forms a pressurizable chamber inside the front end of the shield around the tool at the tunnel face. A conveyor tube longitudinally traverses and has a front end open ahead of the wall in the chamber and is adapted to receive material freed from the tunnel face by the digging tool. An auger can be rotated in the tube to displace freed material back in it from its front end to its rear end. A chute opens upwardly into the rear end of a conveyor tube to receive material therefrom and a pump tube extends longitudinally back from the chute. A piston pump between the chute and the pump tube can displace material from the chute back to the tube. This disclosure recognizes that when driving a tunnel or shaft in soft ground the material that is dug out can be transported relatively easily by a piston pump constructed along the lines of a heavy-duty concrete pump. The tube can be a flexible hose that will not hinder operations behind the machine.
This patent also discloses a piston pump system attached to the conveyor tube that is pressurized by the earth slurry transported therein. The piston pump that drives this slurry through a flexible tube is said to be less cumbersome than the belt type conveyors used in the prior art.
U.S. Pat. No. 4,607,889, issued to Hagimoto et al, pertains to an apparatus for the mixing of a muddying material, such as a bentonite/slurry mix, in the cutterhead assembly. Specifically, rotary mixing means are situated in the outer periphery of the cutterhead chamber and the central portion of the cutterhead chamber. These mixing means rotate at different speeds and opposite directions. Specifically, the mixing means in the central portion rotates faster than that in the outer periphery in order to improve mixing efficiency in the entire chamber. The specific improvement over the prior art is said to be that the central portion of the rear wall of the cutterhead chamber rotates with the cutterhead as opposed to being stable as in the prior art. Consequently, fewer gaskets or seals are needed. In order to regulate the pressure of the muddying material in the cutterhead chamber, a conveyor cylinder having a screw conveyor and filled with muddying material is controlled to remove material from the cutterhead chamber at a variable rate. Slurry or mudding material is transferred from the cutterhead chamber through the tunneling machine through a conventional conveyor cylinder with screw auger. The slurry contained within the conveyor cylinder maintains the desired back pressure.
U.S. Pat. No. 4,456,305, issued to Yoshikawa, provides a shield tunneling machine which comprises a hollow shield main body; a cutter head rotatably disposed at one end of the main body; a pressure chamber formed within the main body immediately behind the cutterhead; an atmospheric pressure compartment formed within the main body in the rear of the pressure chamber; and an earth removing apparatus provided within the main body and holding the pressure chamber in communication with the atmospheric pressure compartment. The earth removing apparatus comprises a tubular casing having, at a front end portion thereof, an earth inlet opening to the pressure chamber, and at the rear end portion thereof a closable earth outlet communicating with the atmospheric pressure compartment, and an earth transport conveyor rotatably provided within the casing and comprising a helically twisted strip. Since the earth transport conveyor has no rotary shaft, the apparatus is capable of transporting and discharging earth containing relatively large solid fragments even when the shield main body or the tubular casing has a reduced diameter.
In this patent disclosure the earth from the workface, which may or may not be slurry, is transferred from the pressure chamber to the atmospheric pressure compartment by a conventional tubular casing having a novel helically twisted strip. The plug of earth in the conventional tubular casing maintains the desired pressure within the tubular casing.
U.S. Pat. No. 4,406,498, issued to Akesaka, teaches a shield tunneling machine in which the shield body comprises a thrust ram or advancing jack and a diaphragm is provided internally across the shield body in a portion spaced apart rearwardly of the front end of the shield body. The diaphragm has an upper opening which is a muck inlet. A bit or scraper is provided in the peripheral portion of the opening. The diaphragm and a member interposed therebetween constitute a casing which defines a muck chamber behind the diaphragm, the muck chamber being usually charged with a liquid. The opening in the diaphragm is an inlet through which the muck is introduced into the muck chamber. The muck inlet is closed and opened by a cover member.
The cover member is coupled to the piston rod of a dual hydraulic piston cylinder device attached to a wall member. A hydraulic pressure circuit for introducing a liquid pressure of a predetermined level into the cylinder retains the piston in a given position within the cylinder so that the cover member normally closes the muck inlet. As long as the pressure of the muck charged between the face and the diaphragm is maintained at a level capable of preventing collapse of the face, more specifically within the range of pressure larger than an active earth pressure in the face ground but smaller than the passive earth pressure thereof, the cover member closes the muck inlet. When the pressure of the muck rises above a predetermined level, the cover member is urged by the muck to open the muck inlet, thereby allowing admission of muck through the inlet. As soon as the muck pressure drops to the predetermined level due to admission of the muck into the muck chamber, then the hydraulic piston cylinder again urges the cover member to its muck inlet closing position.
The muck is discharged from the muck chamber through a muck discharge pipe provided in the casing member in the lower portion of the muck chamber. Discharge of the muck out of the muck chamber is accomplished without changing the muck pressure to a substantial extent and hence without causing collapse of the face.
U.S. Pat. No. 4,165,129, issued to Sugimoto et al, teaches a tunneling machine having a cutter chamber disposed at the front end of a shield frame and driven by cutter drive motors. Sealing members are sealingly disposed between the periphery of the cutter and the front edge of the shield frame. The front end portion of a screw conveyor is placed in the cutter chamber and is sealed in such a way that even when the cutter is driven, the water-tightness of the cutter chamber is maintained. A mucking adjustor for controlling the concentration of the slurry is disposed immediately below an unloading opening at the rear end of the screw conveyor and is communicated through a water supply pipe with a water tank, and through a discharge pipe with a muck-water separator. The muck separated by the separator is transported into a hopper which in turn transports the separated muck to a suitable disposal site. The water separated by the muck-water separator is returned to the water tank for recirculation.
The muck from the face fills not only the cutter chamber but also the screw conveyor through a loading opening so that an uncontrolled flow of the muck from the face to the cutter chamber is prevented. The muck in the cutter chamber is transported by the screw conveyor in a controlled quantity and is discharged through an unloading opening into the mucking adjuster. The muck in the mucking adjuster is agitated with the water charged through the water supply pipe and is discharged through the discharge pipe to the ground surface. The uncontrolled flow of water from the face into the cutter chamber can be prevented by maintaining the pressure of water charged into the mucking adjuster the same as the ground water pressure at the face. Even if the pressure of water charged into the mucking adjuster is changed, the fluctuating pressure is not transmitted to the face by the muck filled in the screw conveyor so that the face is maintained at a stable condition.
As apparent from the state of the prior art, a need exists for a tunneling machine operable in a "closed mode" for soft ground in which the cutterhead is pressurized, and in which low slurry flow is employed to prevent subsistence of an unstable tunnel face by creating a liquid balance without need for high volume recirculation of the slurry and without need for a bulky muck/slurry separation plant, a conventional slurry tunneling systems.
A need also exists for a tunneling machine of the above type in which a fast and convenient conversion can be performed between "closed mode" and "open mode" operation where the cutterhead is not pressurized and competent ground is tunneled.
A need exists as well for a tunneling machine of the above type in which the pressure lock employed in the "closed mode" of operation is a carousel type pressure lock having a substantially constant rate of material processing and a low profile.
A need further exists for a tunneling machine of the above type having an optional secondary separation system in the "closed mode" with hydrocyclone type removal of fines and a simple fresh bentonite addition capability for increased tunnel face stabilization.